The discovery is the result of analysis from two years of the Kepler mission, the space observatory that launched in 2009 and is aimed at discovering other planets in the Milky Way galaxy.

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The research team announced two other significant findings: 1) the majority of planets in our galaxy are small, between the size of Earth and the size of Neptune, and 2) planetary systems, in which multiple planets orbit around one star, are common in our galaxy.

Researchers said they are able to announce such a large number of planets at once because of a new technique for verifying planetary systems.

While the Kepler mission has found what Ames planetary scientist Jack Lissauer called a “motherlode” of astral bodies that could be planets, the process of verifying whether they are planets or stars has been lengthy, mostly involving hours and hours of time looking through telescopes.

Scientists as NASA's Ames Research Center are able to identify planetary systems more quickly than they could before. (NASA)

“It’s been a real bottleneck,” Lissauer said.

But no longer. The research team announced today they have a new technique -- developed at Ames -- for verifying planetary systems that allows them to identify planets by the dozens, rather than one by one.

“We've been able to open the bottleneck to access the motherlode,” Lissauer said, “and deliver to you more than 20 times as many planets as have ever been found and announced at once, previously.”

The new technique involves probability theory and applied math, which is Lissauer’s bailiwick. In essence, it goes like this: About one percent of stars show the slight dimming that suggests something is orbiting around them. Statistically, only one percent of that one percent of stars should reasonably have more than one planet orbiting around them. But Kepler was spotting a few hundred stars with more than one body orbiting them, which is vastly, hugely, more potential planetary systems than should, statistically, exist.

So there must be a reason, Lissauer said.

Now, the other kind of body that could orbit a star is another star. But here's the clue: Star systems are notoriously unstable. A bunch of stars orbiting another star would look like the animation on the right of this video, which resembles the daily life of the average mom, but doesn’t at all resemble the stable planetary system of the animation on the left.

The research team put all this knowledge together with some advanced mathematics and data crunching on the Kepler observations, and out popped—a probability. A number indicating the statistical probability that Kepler was seeing a lot of star systems. It was a very, very low probability. Extremely low. Lower than the threshold required for certainty. It’s the kind of probability I mean when I say I’ll probably write my Christmas thank you notes this weekend: It’s so thoroughly improbable you can go to press with it.

Kepler was not seeing star systems; it was seeing planetary systems. These 715 newly identified planets, NASA researchers can now say, are orbiting around 305 stars, and four of those planets are in the habitable zone.

"Four of the planets are about twice the size of Earth and orbit in their star's so-called habitable zone," NPR's Nell Greenfieldboyce reports for our Newscast unit, "where temperatures might be suitable for liquid water."

Researchers will now turn to the next two years of Kepler data, and expect to be able to announce hundreds more planets in future years.